Resilient mounting for pulverizer grinding rings



RESILIENT MOUNTING FOR PULVERIZER GRINDING RINGs' Filed Oct. 51, 1947 L. L. LEAC H May 6, 1952 2 SHEETS'.SHEET 1 o I O w 2 2 G 8 z Q J 00 a w 3 J1 L U ..L:...L' il nu w n 3 2, 2 J Md l i you. 3 m

I INVENTOR L aster Ll each @m ATTORNEY M y 1952 L. L. LEACH 2,595,587

RESILIENT MOUNTING FOR PULVERIZER GRINDING RINGS 7 Filed Oct. 31, 1947 2 SHEETS-SHEET 2 INVENTOR Lesterll e'ac/I ATTORNEY a rigid spring support.

Patented May 6, 1952 RESILIENT MOUNTING FOR PULVERIZER GRINDING RINGS Lester L. Leach, Barberton, Ohio, assignor to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application October 31, 1947, Serial No. 783,248

6 Claims.

1 The present invention relates to the construction and operation of pulverizers of the type in which materials, such as coal, rock, and the like,

are pulverized between one or more grinding surfaces and a relatively moving rolling grinding element or elements. A pulverizer of this general type is shown in U. S. Patent No. 2,275,595, in which the pulverizing elements are relatively movable upper and lower grinding rings between which a circular row of grinding balls is horizontally arranged.

In such pulverizers one of the rings is rotated while the other ring is maintained in a substantially non-rotative position. The grinding balls move in a circular path between the rotating and non-rotative rings with the grinding surfaces therebetween in contact under the influence of a positive pressure. Heretofor, the grinding pressure has usually been obtained by a plurality of multi-coil springs arranged to exert a controlled compressive pressure upon the non-rotative ring, although this has not been imperative in all constructional arrangements. It has also been customary to limit the rotational movement and maintain the non-rotative ring in proper position by guide members mounted upon the pulverizer housing and arranged to engage lugs projecting outwardly from the circumference of the ring. With this arrangement the ring is capable of vertical movement within the guides, as restricted by the compressive force of the pressure springs, while the ring is incapable of substantial rotational movement. The contacting surfaces of the ring lugs and the guide members are protected by wearing plates, but frequently the cost and inconvenience of maintaining and replacing the wearing plates has been greater than desired. The guide members further form an obstruction to the movement of material between the outer circumference of the non-rotative ring and the pulverizer housing. This is particularly apparent in air-swept pulverizers using air classification for producing the desired fineness of finished product wherein the guide assembly obstructs the flow of material through the pulverizer.

In accordance with the present invention I avoid the use of wearable guides to limit the rotational movement of a non-rotary grinding ring in a pulverizer. This is accomplished by the use of a torsion spring which is secured at one end to the non-rotary ring and at its opposite end to The spring support is mounted on the pulverizer housing and is arranged for adjustable movement in a vertical direction. With this construction the spring may be compressed to provide an adjustable downward pressure upon'the non-rotary ring while the torsional force of the spring is exerted in a generally horizontal plane to restrain the tendency for the non-rotary grinding ring to rotate in the direction of the moving grinding parts. Any tendency on the part of the non-rotary grinding ring to shift in a radial direction due to the grinding effects in the pulverizer will also be restrained by the use of a plurality of such springs arranged circumferentially of the non-rotary ring.

The principal object of the present invention is to provide apparatus of the type described which is characterized by an improved construction and arrangement of apparatus for applying a restraining force to limit the motion of non-rotary pulverizing parts and for applying a resilient pressure to the grinding surfaces of a pulverizer. A further and more specific object is to provide a resilient means for limiting the rotational movement of a non-rotary grinding surface in a pulverizer. An additional specific object is to provide a resilient means for restraining the radial movement of a non-rotary pulverizer part. Another object is to provide a resilient restraining support for a non-rotary part of a pulverizer grinding zone which is characterized by a low first cost, low maintenance and a minimum obstruction to the flow of material through the pulverizer.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use. reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described an embodiment of my invention.

Of the drawings:

Fig. 1 is an elevation View, in section, of a pulverizer incorporating the present invention;

Fig. 2 is a plan view, partly in section, showing the relationship of the present invention to the adjacent parts of the pulverizer, as viewed from line 2-2 of Fig. 1;

Fig. 3 is an enlarged elevation view, in section, of a portion of the apparatus shown in Fig. 1; and

Figs. 5 and 6 are cross-sections taken on the lines li, 5-5 and 6-6, respectively, of Fig. 3.

In general, the pulverizer illustrated includes a cylindrical upper housing and a lower section I I supported on a foundation l2. The lower section encloses the pulverizer gear drive which includes a horizontal pinion shaft l3 arranged to drive a vertical drive shaft [4 axially arranged in the section II and the housing 10. The drive shaft l4 extends upwardly through bearings arranged in a base plate l5 forming the top of the base section I I. The upper housing IE] is detachably secured to the base plate l5 and encloses the grinding parts of the pulverizer which comprises a drive yoke ll of generally conical form keyed on the upper part of the drive shaft I 4 and an annular grinding ring [8 supported on and dowelled to a flattened lower portion of the drive yoke. The upper face of the grinding ring is shaped to form a circular track for a row of rolling grinding elements 20, preferably balls of wear resistant alloy. The balls support a nonrotary upper grinding ring 2| having a circular ball track formed in its lower face. An annular spider 22 is mounted upon and dowelled to the upper ring and is provided with a plurality of sockets for the insertion of springs 23, as hereinafter described, for exerting a resilient downward grinding pressure on the grinding parts. The springs 23 engage individual vertical adjusting bolts 24 supported by a sleeve or bracket 25 which is affixed to the cover plate 26 of the housing Isl. The springs 23 not only provide a resilient compressive force for the application of a grinding pressure upon the pulverizing parts, but also provide a resilient torsional force restraining the rotational and radial movement of the ring 2| relative to the axis of the ring H3.

The material to be pulverized is supplied by a feeder 21 through a feed spout 28 to the inner side of the upper grinding ring 2| and the circular row of balls 20 and falls on the upper inclined surface of the yoke ll. The inclined surface of the yoke and the rotation thereof distributes the material circumferentially into the grinding area. Due to the effect of centrifugal force the material tends to flow outwardly between the rings 18 and 2| and balls 20, and to discharge therefrom at an oblique angle to the periphery of the grinding elements. The angle of discharge depends upon the rotational speed of the lower ring.

The pulverizer illustrated is of the air-swept type wherein a stream of primary or carrier air passes upwardly at the circumferential discharge side of the pulverizer grinding zone and through a rotary classifier 30 to an outlet 3| in the top of the housing. The air is normally preheated and supplied under pressure by a suitable forced draft fan (not shown) through a connecting duct and an inlet to an annular wind box 32 surrounding the lower part of the housing section I0. The air passes through passages 33 into the housing and then fiows upwardly through a throat passage 34 formed between the lower grinding ring I8 and an annular throat ring 35 mounted on the side of the housing [9. Thus solid materials are pulverized in a grinding zone under the influence of a controlled grinding pressure, air classified within the pulverizer housing, and then delivered to point of use in a carrier stream of air.

As shown particularly in Figs. 2-6, the present invention includes a circumferentially spaced series of springs 23 attached to and bearing on the spider 22 and arranged to exert a controlled pressure upon the pulverizer grinding surfaces. Each spring 23 is shaped from a length of spring steel bar stock. The metal is bent to form a single complete coil turn 35 having a pitch diameter as large as possible while providing an installed clearance with respect to the rotating parts of the pulverizer. The coil turn is symmetrically formed about its coil diameter to have a free length or gap 39 between opposite ends of the turn less than the pitch diameter of the coil. For example, a free length of the gap 39, as measured between the ends of the coil, of from to A; the pitch diameter of the coil has been used. Thus with a 1%" spring steel bar cross sectional diameter, and a coil pitch diameter of 13 inches, the gap 39 between opposite ends of the coil turn may have, for example, a free length of approximately 4 inches. The ends 3'! and 33 of the coil beyond the completed coil turn are bent in opposite directions parallel to the axis of the coil turn and to have a common axis, which is upright when the spring is installed in the pulverizer.

The spider 22 is provided with a series of lugs or projections 40 cast on the outer circumference thereof corresponding with the position of the springs. The number of springs and the corresponding spider projections depends upon the size of the pulverizer and will usually consist of 4, with a spacing therebetween. Each spider projection is provided with a pocket or recess 4| machined to a close tolerance for a close fit with the end 3'! of a spring which is inserted therein. A set screw 42 is provided to lock the spring end 31 in the recess 4|.

The opposite upper end 38 of each spring is inserted into a close fitting socket 43 formed in a socket member or cap 44 which is keyed to the end of the vertically adjustable bolt 24. Although the compressive force of the spring, when in its operating position, will insure the maintenance of the spring end in the socket, a set screw 46 is provided in the Wall of the cap to anchor the spring end 38 in its socket. The cap 44 is further provided with a recess 41 having its axis parallel to and spaced from the socket 43 and opening upward to receive the end of the bolt 24. A key 48 is riveted in place in the recess to engage a corresponding keyway 59 which is cut longitudinally of the bolt. Thus the cap is fixed in its radial relationship to the bolt. The bolt is threaded for a substantial portion of its upper end 5! while the keyway 50 extends for a substantial portion of its lower portion 52. The hollow sleeve or bracket 25 has a flanged upper end 53 which is bolted to the outer side of cover plate 26 of the housing Ill. The bracket projects through an opening in the plate 26 to a spaced position within the pulverizer. The hollow portion of the bracket has an internal diameter exceeding the diameter of the bolt 24 and at its lower end is provided with a shoulder 54 which encircles the bolt in a sliding fit. The bracket is further provided with a key 55 which is riveted in place and engages the keyway 50 of the bolt 24. With this construction the bolt is protected from abrasion by airborne solid materials circulated through the interior of the housing l0, and is restricted to a straight line vertical movement within the bracket. The shoulder 54 at the lower end of the bracket tends to prevent the movement of abrasive pulverized material into the annular space or chamber 56 between the bolt and the interior of the bracket. As a further protection to the bolt, and the threads on the upper end 5| thereof a lubricant, such as grease, is forced under pressure into the annular .5 chamber 56 through a fitting 51 positioned on the exterior of the housing H1.

The vertical movement of the bolt is obtained by adjustment of a threaded nut 55. The nut 58 is hollow and internally threaded throughout its length to engage the threaded portion of the bolt 24. Its exterior surface is machined to form a lower flange 6B of circular cross-section which is closely fitted into a correspondingly machined annular recess in the flange 53 of the bracket 25 where the inner face of the nut flange 60 lies in a horizontal plane common with the outer face of the flange 53. The intermediate portion |6| of the nut is also machined to a circular crosssection having a diameter somewhat less than the flange 60 portion of the nut. This intermediate portion is closely fitted by an annular retainer member 62 which is bolted by socket head bolts 63 to the flange 53 of the bracket. With the upper end portion 64 of the nut formed as a standard hex-headed nut to receive the jaws of an adjusting wrench, the nut 58 is rotated to cause a vertical movement of the bolt 2d.

With the mechanism described, the bolt 24 may be vertically positioned by rotational adjustment of the nut 58. The compressive pressure exerted by the springs is proportional to their deflection as measured by the dimension of the gap 39. The bolt 24 in its vertical movement is displaced without radial movement by reason of the key 55 in the supporting bracket 25 engaging the keyway 50 of the bolt 24. Thus the spring 23 will be compressed, or the pressure thereon released, depending upon the vertical position of the cap 44 relative to the spider 22. The lineal vertical movement of the bolt in adjusting the pressure exerted by the spring is advantageous in that the spring 23 will not be under a torsional pressure by reason of cap 44 rotation which would tend to either increase or decrease the pitch diameter of the spring coil turn 38. Therefore the pressure exerted upon the grinding elements can be suitably adjusted to compensate for ring and ball wear without altering the restraining forces exerted by the springs in the plane normal to the coil axes.

When the pulverizer is started, the rotation of the lower ring I8, with the companion movement of the balls 20 in their circular path, tends to cause the upper ring 2| to rotate in the same direction due to the friction or drag between the grinding surfaces. This rotational tendency on the part of the top ring 2| creates a stress on the springs 23, with the springs permitting a slight initial top ring movement due to spring elasticity. With the forces tending to rotate the top ring being greatest during initial rotation of the lower ring, because of friction factors between rings and balls, and the inertia of the related parts, the forces exerted on the springs will decrease as the rotating parts attain their design speed. Thus the springs will return the top ring to a position intermediate its non-operating and starting location. The described movement of the upper ring is small and hardly noticeable to the eye, but can be measured at the circumference of the upper ring 2| in small fractions of an inch. The extent of the movement of the top ring in a rotational direction is determined by a balance of the forces acting thereon wherein the moving force resulting from friction between the ring and the balls is balanced by the counteracting resilient force exerted by the springs. Abrupt or gradual changes in the balance between these opposing forces permit slight movements of the upper ring without the shock effects of ring stops striking fixed guide members. Such shock effects would result in wear between the surfaces in contact, and unnecessary noise.

As solid materials are delivered to the pulverizer by the feeder 21 the material is ground by the material passing between the grinding surfaces of the rings and balls. As a result the upper rin 2| is subjected to a variety of forces tending to move the top ring against the restraining forces of the spring. For example, an obstruction in the grinding race of the pulverizer, such as an unusually hard piece of the material being ground or of foreign material, may momentarily force the balls to pass over or partially around the obstruction. Such circumstances will force the top ring upwardly at one side against the compressive force of the adjacent springs. Simultaneously the obstruction may tend to force the top ring laterally out of its axial position. The springs, however, tend to and will return the ring to its initial position since the crushing effect of the grinding elements and the spiral movement of the grinding balls will either crush the material under the influence of the increased grinding pressure exerted by the springs, or will force the obstruction out of the grinding race. Thus, the spring'arrangement of the present invention provides a floating mounting for the top ring which is capable of maintaining 'the ring substantially in a non-rotative position while permitting a flexibility in the mounting which allows the grinding zone to give without breakage or excessive wear.

It will also be noted that the single coil turn of the springs in their attachment to, the upper ring spider and the means for adjusting the compressive pressure upon the grinding elements provide a minimum obstruction to the movement of ma terials through the pulverizer. This is particularly true in the annular space between the upper grinding ring 2| with its spider attachment 22, and the pulverizer housing l0.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form of the invention now known to me, those skilled in the art will understand that changes may be made in the form of th apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

I claim:

1. A pulverizer comprising a housing, a bottom ring within said housing arranged for rotation about a vertical axis and having an upper annular grinding surface, a plurality of rolling grinding elements in contact with said grinding surface, an upper ring having a lower annular rinding surface in contact with said rolling grinding elements, and means for simultaneously exerting a resilient compressive pressure upon said rings and rolling grinding elements and exerting a torsional pressure for maintaining said upper ring in a non-rotative position centrally of said vertical axis including, a plurality of brackets affixed to said housing at equally spaced positions about said axis of rotation, a threaded bolt projecting vertically through each of said brackets, a vertical keyway in each bolt, a key positioned in each bracket to engage said keyway, a nut engaging said threaded bolt for vertical adjustment thereof, and a coil spring having one end affixed to each of said bolts and its opposite end affixed to said ring at circumferentially equally spaced positions.

2. A pulverizer comprising a housing, a, plurality of grinding elements within said housing arranged for rotational movement in a circular path between and in contact with opposed complementary grinding surfaces, means for rotating one of said surfaces about the axis of said circular path, and resilient spring means simultaneously exerting a positive pressure normal to said grinding surfaces and forming the sole means resisting rotational movement of the other of said grinding surfaces including an adjustable support associated with said housing and movable in a direction parallel to the axis of said circular path, means for rigidly anchoring one end of said spring means to said adjustable support, and means for rigidly locking the opposite end of said spring means to the other of said grinding surfaces.

3. A pulverizer comprising a housing, a plurality of grinding elements arranged for rotational movement in a horizontal circular path between the grinding surfaces of opposed grinding rings, means for rotating one of said rings about the axis of said circular path, and means for simultaneously exerting a downward pressure normal to and solely resisting rotation of the other of said grinding surfaces comprising a coiled spring positioned between and having its opposite ends rigidly connected to said other ring and housing.

4. A pulverizer comprising a housing, upper and lower grinding rings in said housing, a row of rolling grinding elements positioned on said lower ring and arranged to support said upper ring, means for rotating said lower ring, said upper ring being free to rotate on said rolling grinding elements, and means for simultaneously exerting a downward pressure normal to and solely resisting rotation of said upper grinding ring comprising a coiled spring having its end portions extended in opposite directions parallel to the coil axis, one end of said spring rigidly locked in position relative to said upper ring, and the opposite end of said spring rigidly anchored in a horizontally fixed vertically adjustable position relative to said housing.

5. A pulverizer comprising a housing, upper and lower grinding rings in said housing, a row of rolling grinding elements positioned on said lower ring and arranged to support said upper ring, means for rotating said lower ring, said upper ring being free to rotate on said rolling grinding elements, and means for simultaneously exerting a downward pressure normal to and solely resist ing rotation of said upper grinding ring comprising a single turn coil spring having its end portions extended in opposite directions parallel to the coil axis and from the outer circumference of the coil, one end of said spring rigidly locked in position relative to said upper ring, and the opposite end of said spring rigidly anchored in a horizontally fixed vertically adjustable position relative to said housing in initial vertical alignment with the locked position of said spring and ring,

6. A pulverizer comprising a housing having a top cover plate with an airborne pulverized material outlet therein, a plurality of grinding elements arranged for movement in a. horizontal circular path, a lower grinding ring supporting said grinding elements, means for rotating said lower grinding ring about a vertical axis, an upper grinding ring supported by said grinding elements, a throat ring encircling the outer periphery of said lower grinding ring in spaced radial relationship and defining a circumferential throat therebetween for the upward admission of carrier air, and a plurality of single turn coil springs circumferentially spaced about said upper grinding ring and constituting the sole means resisting rotation of said upper ring, each spring having its end portions extended in opposite directions parallel to the coil axis and from the outer circumference of the coil turn, one end of each spring being rigidly locked in position relative to said ring and the opposite end of the spring anchored to a horizontally fixed vertically adjustable position relative to said housing, With the opposite ends of the coil initially in vertical alignment and the coil axis positioned between the coil ends and the axis of lower ring rotation.

LESTER L. LEACH.

REFERENCES CETED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 153,049 Comins July 14, 1874 821,421 Kitto May 22, 1906 1,499,624 Middelboe July 1, 1924 1,774,340 Thurmann Aug. 26, 1930 2,214,832 Hobbs Sept. 17, 1940 2,389,844 Ebersole Nov. 27, 1945 FOREIGN PATENTS Number Country Date 578,313 France June 28, 1924 543,769 Germany Feb. 10, 1932 

